The opening talk as DrupalCamp Paris 2019 was a presentation given by Thomas Jolliet (FranceTV) and yours truly about how we rebuilt FranceTV Sport to a Symfony 4 / headless Drupal 8 combo.
The most salient points of the talk are probably the "defense in depth" mechanisms we built for scalability and fault tolerance, and the business results, like -85% full page load time, -65% speed index, or +50% iOS app traffic.